Barotrauma

Tissue injury caused by pressure differences between an air space in the body and the surrounding water, most often affecting ears, sinuses, mask, or lungs.

Barotrauma is any injury caused by a pressure imbalance between a gas space and the surrounding environment. Underwater, Boyle's law means air spaces shrink on descent and expand on ascent, and if a diver cannot equalize a space, the pressure difference stresses the tissue around it. The middle ear is by far the most common site, followed by the sinuses, the air space inside the mask, teeth with trapped air under fillings, and, most seriously, the lungs.

Descent barotrauma, often called a squeeze, happens when a blocked Eustachian tube or congested sinus cannot admit air: the eardrum bows inward, blood vessels leak, and continuing down can rupture the drum. Ascent barotrauma is the reverse. Expanding air that cannot escape causes a reverse block in ears or sinuses, and breath-holding on ascent can cause lung overexpansion injury, the most dangerous form, which may force gas into the chest or bloodstream as an arterial gas embolism.

Prevention is straightforward: equalize early and often, never dive congested, descend and ascend slowly, and never hold your breath on scuba. Symptoms like ear pain, blood in the mask, muffled hearing, or dizziness after a dive deserve a doctor's attention, and DAN's medical line is a good first call. Write down the dive details while they are fresh, depths, times, and when the symptoms started all help the physician assess what happened.